Thank's a lot jkahrs! That was definetly the problem on the XP machine, now it run's fine with the PicoScope 6.6.23.2. I also found out that from time to time, the Oscilloscope was not recognize and was saw as an "unknow usb device" and the Picoscope software will just automatically eject it. On the...

Thank's for your anwser, unfortunatly I'm sure that the drivers are from the Picoscope and not window's default. I followed this toturial (http://www.instructables.com/id/Windows ... /?ALLSTEPS)

Yes sorry for that, is the 32bit version of XP